Seven students from Darmstadt University’s Lichtwiese campus south of Frankfurt, Germany were victims of an attempted poisoning, the school revealed, though they are all recovering smoothly at a nearby hospital. German police began investigating the attempted murder on Tuesday, Aug. 24, after students started showing up to the hospital with similar symptoms.

According to BBC News, the students had all eaten from a small kitchen at the Lichtwiese campus where they are believed to have ingested a harmful substance that was added to either the milk cartons or the water bottles, which were freely accessible to anyone.

The investigators said that they know what kind of poison was used, but have refused to reveal its name to the press at the time. The chemical is noted for having a “pungent smell,” however, which would have presumably been noticed by the students before ingesting the beverages.

One 30-year-old student reportedly had the worst effects from the poison, and was in critical condition, but the hospital said that they would be recovering fine with the other inflicted students. Everyone is reported to be feeling much better, with the remaining two students still being treated by the hospital set for release by the end of today. No other students have reported any of the same poisoning symptoms since the original seven’s arrival this morning.

“Big relief! All poisoning victims are feeling better!” the University said on Twitter, updating all who were concerned. “The last two affected members can also leave the hospital today.”

The building that the students were eating in was the Department of Materials and Geoscience tea area, which teaches classes involving the proper use and technology of recycling and reusing materials.

“I wish the affected all the best, a quick recovery and can assure them my full support,” said Science Minister Angela Dorn-Rancke. “Together with the university and investigators, we now need to clarify the situation as quickly as possible.”

Investigators believe that the building was targeted over the weekend, and even warned students that they should seek medical treatment if they, “feel unwell or their extremities show a bluish discoloration.” All seven affected students who received treatment at the hospital reported this bluish discoloration in their toes and fingers.

It has yet to be identified what poison was used, why the poison probe investigators at Darmstadt University knew that bluish discoloration would be a symptom of the poisoning, or why these students were the ones affected. One burning question remains: if the building was known to have an active poison probe in effect, why were the students allowed to eat in the tea room in that building?

Police have searched nearby buildings at Darmstadt University as a precaution, NPR reported, but found zero trace of anything that would be connected to poisoning in the Materials Science building.

As far as authorities have said, no motive has been established, and no suspects have been questioned. They are working to “identify the culprit or culprits,” and report no “acute danger” lingering in the area. Prosecutor Robert Hartmann told the press that they believe that the poisoning was “deliberate,” but have no solid information to back up the theory at this time. The poison probe, however, is being referred to as a “poison attack.”

A homicide squad with over 40 detectives has been placed on the scene, The Guardian reports, with “investigations running at high speed.”

Darmstadt University President Tanja Brühl was “shocked” at the crime that took place on campus, releasing a statement offering sympathies to all who were affected. The President said that they would “get in touch with them as soon as possible, their condition allowing.”